In recent years, much attention has been paid to the reduction of rollover in motor vehicles, especially in larger vehicles such as sport-utility vehicles (SUV's) which have a relatively high center of gravity. These vehicles may experience friction induced rollover conditions, in which the vehicle can rollover in response to friction forces acting on the vehicle tires, without striking an obstacle. Vehicle rollover is caused by exceeding the critical roll angle for a particular vehicle. The roll angle is a function of the suspension of the vehicle, the vehicle's loading condition and other vehicle characteristics and dynamic conditions. For example, in a steady state driving condition the roll angle is proportionally related to the amount of lateral acceleration, the suspension tuning, and the dimensions of the vehicle (i.e. track width divided by the height of center of gravity). In transient maneuvers, the critical roll angle is somewhat variable and is determined by the additional factor of steering angle. In both cases, the roll angle behaves as a second order system to the input of lateral acceleration.
Existing rollover protection systems employ some form of a predictive means in an attempt to predict rollover and therefore prevent the same through corrective action such as vehicle braking, engine throttling or steering intervention. For example, some systems will directly monitor the roll rate or the roll acceleration in an effort to predict rollover. However, these systems do not take into account the primary cause of vehicle rollover, i.e. lateral acceleration. Other systems monitor the lateral acceleration in an effort to predict rollover. For example, some systems will monitor the change rate of the lateral acceleration as a predictor of vehicle rollover. Unfortunately, the change rate of lateral acceleration is not the best predictor of rollover and may only provide small period of time to take corrective action.
Accordingly, there exists a need to provide an active rollover protection system that prevents vehicle rollover utilizing a predictor that is both accurate and provides greater time to take corrective action to reduce the risk of vehicle rollover.